Generally, since an electronic paper uses a reflective display having a memory function, it does not require a light source needed for a conventional liquid crystal display device and it does not require continuous power consumption as required in OLED, it can be driven with low power.
Current representative methods for expressing electronic paper display include (i) an electrophoretic method (E-INK, SiPix), whether colored charged particles, which have been mixed in oil, are stored in microcapsule or not, which enables the charged particles to respond to application of an electric field (ii) a twist ball method (Gyricon media), which rotates spherical particles consisting of top and bottom hemispheres having opposite charges and different colors by using an electric field, (iii) a QR_LPD method (Quick Response-Liquid Powder Display, Bridgestone), which operates charged particles under a dry environment, and (iv) a liquid crystal display method (Kent Display) using selective reaction of cholesteric liquid crystal molecules.
Among the methods, the electrophoretic method is the most representative for electronic paper display. Particles used for electronic paper display of the electrophoretic method have permanent charges. However, particles having permanent charges have high driving voltage, a slow response speed, and difficulty in gradation expression. In addition, in order to realize a digital image, an active matrix addressing (AM addressing) driving method, which separately provides a switching device and a capacitance device such as a transistor and a diode for each pixel to record necessary information for each pixel, should be used. To the end, an expensive thin film transistor (TFT) array backplane apparatus is required.
In case of an electronic paper of the cholesteric liquid crystal display method, a passive matrix (PM) addressing driving method, which does not separately require the switching device and the capacitance device, may be used. However, image quality is deteriorated compared to the active matrix addressing driving method, and a high resolution large scale panel cannot be driven.